Correct upstream connection closing

[const-t]

Commit ef12112

Looking this code I can assume following behavior: When error occurred, Tempesta sends error response, however if at this moment new segment will be received it will be passed to tfw_connection_recv() and again to tfw_http_resp_process() that not expected at this moment. Seems here we should mark connection as Conn_Stop.

Need to develop the new test for this issue. The test:

1. Send 3 requests from 3 different clients.
2. Prepare 3 pretty large responses. First one invalid, for instance with invalid header.
3. Send 1 byte segmented response to Tempesta.
4. Check the first client received valid response and that connections with another two clients was closed.

Also case T_BLOCK in this place looks strange, because tfw_http_parse_resp() must doesn't return T_BLOCK. Please check it out.